In reply to Drew52:
You should be bird free after July 31 as for most coastal climbs.
I made the mistake of climbing old Man of Hoy OMOH in June . Had to throw away my jacket and also got amoebic dysentery (or similar) from bird puke.
With regard to the OMOS check tides and times well beforehand. You may be able to walk across to set the Tyrolean instead of talking your mate into swimming the channel.